Side impact airbag systems

ABSTRACT

A variable inflation rate inflator system for inflating one or more airbags including an inflator for releasing a gas into the airbag(s), a first anticipatory crash sensor for determining that a crash requiring an airbag will occur based on data obtained prior to the crash and, upon the making of such a determination, triggering the inflator means to release gas into the airbag(s) to thereby inflate the same at a first inflation rate, and a second crash sensor for determining that a crash requiring an airbag will occur or is occurring and, upon the making of such a determination, affecting the inflator such that an additional quantity of gas is released thereby into the airbag(s) to thereby inflate the airbag(s) at a second inflation rate greater than the first inflation rate. Also, an airbag passive restraint system for protecting an occupant sitting in the seat adjacent the side door is disclosed including at least one airbag arranged to be inflated between the occupant and the side door, a sensor for detecting that a crash requiring deployment of the airbag(s) is required, an inflator for releasing a gas into the airbag(s) to inflate the same and which is triggered by the sensor to release gas into the airbag(s) in response to the detection by the sensor of a crash requiring deployment of the airbag(s), and a system for permitting the occupant to be displaced away from the side door upon inflation of the airbag(s) and thereby increase the space between the occupant and the side door.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent application Ser. No. 08/247,760 filed May 23, 1994 abandoned.

BACKGROUND OF THE INVENTION

Frontal impacts are the number one killer of vehicle occupants in automobile accidents with about 16,000 fatalities each year. Side impacts are the second cause of automobile related deaths with about 8,000 fatalities each year. The number of fatalities in frontal impacts is now decreasing due to the introduction of airbags and mandatory seatbelt use laws. It is natural now that a considerable effort be applied to saving lives in side impacts.

Several automobile manufacturers are now considering the use of side impact airbags to attempt to reduce the number of people killed or injured in side impacts. The side impact problem is considerably more difficult to solve in this way than the frontal impact problem due to the lack of space between the occupant and the side door and to the significant intrusion of the side door into the passenger compartment which typically accompanies a side impact.

Some understanding of the severity of the side impact problem can be obtained by a comparison with frontal impacts. In the Federal Motor Vehicle Safety Standard (FMVSS) 208 49 kph crash test which applies to frontal impacts, the driver, if unrestrained, will impact the steering wheel at about 30 kph. With an airbag and a typical energy absorbing steering column, there is about 40 cm to about 50 cm of combined deflection of the airbag and steering column to absorb this 30 kph difference in relative velocity between the driver and vehicle interior. Also, there is usually little intrusion into the passenger compartment to reduce this available space.

In the FMVSS 214 standard crash for side impacts, the occupant, whether restrained or not, is impacted by the intruding vehicle door also at about 30 kph. In this case there is only about 10 to 15 cm of space available for an airbag to absorb the relative velocity between the occupant and the vehicle interior. In addition, the human body is more vulnerable to side impacts than frontal impacts and there is usually significant intrusion into the passenger compartment. A more detailed discussion of side impacts can be found in a paper by Breed et al, “Sensing Side Impacts”, Society of Automotive Engineers No. 940651, 1994, which is included herein by reference.

Ideally, an airbag for side impact protection would displace the occupant away from the intruding vehicle door in an accident and create the required space for a sufficiently large airbag. Sensors now being used for side impact airbags, however, begin sensing the crash only at the beginning of the impact at which time there is insufficient time remaining to move the occupant before he is impacted by the intruding door. Even if the airbag were inflated instantaneously, it is still not possible to move the occupant to create the desired space without causing serious injury to the occupant. The problem is that the sensor that starts sensing the crash when the impact has begun, is already too late, i.e., once the sensor detects the crash, it is usually too late to properly inflate the airbag.

There has been discussion over the years in the vehicular safety community about the use of anticipatory sensors so that the side impact accident could be sensed before it occurs. Heretofore, this has not been practical due to the inability to predict the severity of the accident prior to the impact. A heavy truck, for example, or a tree is a much more severe accident at low velocity than a light vehicle or motorcycle at high velocity. Until now, it has not been possible to differentiate between these different accidents with a high degree of certainty.

Once a sufficiently large airbag is deployed in a side impact and the driver displaced away from the door and the steering wheel, he will no longer be able to control the vehicle that could in itself cause a serious accident. It is critically important, therefore, that such an airbag not be deployed unless there is great certainty that the driver would otherwise be seriously injured or killed by the side impact. Anticipatory sensors have heretofore not been used because of their inability to predict the severity of the accident. As discussed more fully below, the present invention solves this problem and therefore makes anticipatory sensing practical. This permits side impact airbag systems that can save a significant percentage of the people who would otherwise be killed as well as significantly reducing the number and severity of injuries. This is accomplished through the use of pattern recognition technologies such as neural networks such as discussed in co-pending patent application Ser. No. 08/640,068 filed Apr. 30, 1996 which is a continuation of U.S. patent application Ser. No. 08/239,978 filed May 9, 1994, now abandoned.

Neural networks are capable of pattern recognition with a speed, accuracy and efficiency heretofore not possible. It is now possible, for example, to recognize that the front of a truck or another car is about to impact the side of a vehicle when it is one to three meters or more away. This totally changes the side impact strategy since there is now time to inflate a large airbag and push the occupant out of the way of the soon to be intruding vehicle. Naturally, not all side impacts are of sufficient severity to warrant this action and therefore there will usually be a dual inflation system as described in more detail below.

Although the main application for anticipatory sensors is in side impacts, frontal impact anticipatory sensors can also be used to identify the impacting object before the crash occurs. Prior to going to a full frontal impact anticipatory sensor system, neural networks can be used to detect many frontal impacts using data in addition to the output of the normal crash sensing accelerometer. Simple radar or acoustic imaging, for example, can be added to current accelerometer based systems to give substantially more information about the crash and the impacting object than possible from the acceleration signal alone.

The side impact anticipatory sensor of this invention can use any of a variety of technologies including optical, radar, acoustical, infrared or a combination of these. The sensor system typically contains a neural network processor to make the discrimination however a simulated neural network, a fuzzy logic or other algorithm operating on a microprocessor can also be used.

SUMMARY AND OBJECTS OF THE INVENTION

This invention comprises an anticipatory sensor system which uses (i) a source of radiant energy either originating from or reflected off of an object or vehicle which is about to impact the side of a target vehicle, plus (ii) pattern recognition means to analyze the radiant energy coming from the soon-to-be impacting object or vehicle to (iii) assess the probable severity of a pending accident and (iv) if appropriate, inflate an airbag prior to the impact so as to displace the occupant away from the path of the impacting object or vehicle to create space required to cushion the occupant from an impact with the vehicle interior. Although the primary area of application of this invention is for protection in side impacts, the invention also provides added protection in frontal impacts by reducing the incidence of injury to out-of-position occupants by permitting a slower inflation of the airbag and displacing the occupant away from the airbag prior to the impact.

The principal objects and advantages of this invention are:

1. To provide for the enhanced protection of occupants in side impacts by determining the probable severity of a pending accident and inflating an airbag prior to the impact to displace the occupant away from the vehicle door.

2. To provide for a method of identifying and classifying an object which is about to impact a vehicle.

3. To adapt pattern recognition techniques, and particularly neural networks, to permit the identification of objects external to an automotive vehicle and the determination of their approach speed and angle of potential collision.

4. To provide a method for assessing the probable severity of a pending accident based on the identification of the class of an object which is about to impact the vehicle plus stored information about the class of such objects such as its mass, strength and attachment to the earth.

5. To provide a method using an ultrasonic system for use in illuminating an object which is about to impact a vehicle and using the reflection of the ultrasonic illumination in combination with a pattern recognition system to identify the object.

6. To determine the approach velocity of an object which is about to impact a vehicle.

7. To identify that a truck is about to impact a vehicle.

8. To identify that an automobile is about to impact a vehicle.

9. To identify that a vehicle is about to impact with a tree.

10. To provide a method using an electromagnetic wave system for use in illuminating an object which is about to impact a vehicle and using the reflection of the electromagnetic wave illumination in combination with a pattern recognition system to identify the object.

11. To provide a method using an the passive infrared electromagnetic waves radiating from an object such as a motor vehicle in combination with a pattern recognition system to identify the object.

12. To provide a system for identifying an object which is about to impact a vehicle in a substantially side impact.

13. To provide a system for identifying an object which is about to impact a vehicle in a substantially frontal impact.

14. To provide a system comprising a variable inflation airbag system where the control of the inflation of the airbag is determined by an prediction of the probable severity of an accident prior to the accident occurring.

15. To provide apparatus for inducing slack into a seatbelt in the event of a side impact to permit the occupant to be displaced sideways in the vehicle.

16. To provide for a single airbag module for protection of the head and torso of an occupant in side impacts.

17. To provide a single airbag module for mounting in the seat back of a vehicle for the protection of the head and torso of an occupant in side impacts.

18. To provide a structure and method for moving the occupant and his seat in the event of a side impact accident to increase the space between the occupant and the intruding object.

19. To provide for an airbag to be deployed external to the vehicle in conjunction with an anticipatory sensor in side impacts.

20. To provide a method using an ultrasonic wave system for use in illuminating an object which is about to impact a vehicle and using the reflection of the ultrasonic wave illumination in combination with a pattern recognition system to identify the object.

The variable inflation rate inflator system for inflating one or more airbags in accordance with the invention comprises inflator means for releasing a gas into the airbag(s), a first anticipatory crash sensor for determining that a crash requiring an airbag will occur based on data obtained prior to the crash and, upon the making of such a determination, triggering the inflator means to release gas into the airbag(s) to thereby inflate the same at a first inflation rate, a second crash sensor for determining that a crash requiring an airbag will occur or is occurring and, upon the making of such a determination, affecting the inflator means such that an additional quantity of gas is released thereby into the airbag(s) to thereby inflate the same at a second inflation rate greater than the first inflation rate.

The inflator means may comprise a first and second inflator structured and arranged to produce gas and direct the gas into the airbag(s) and which are independent of one another such that the first inflator may be triggered by the first anticipatory sensor without triggering of the second inflator and the second inflator may be triggered by the second crash sensor without triggering of the first inflator.

In conjunction with the variable inflation rate inflator system described above, a method for providing a variable inflation rate of one or more airbags is also envisioned. Such a method would entail determining that a crash requiring an airbag will occur based on data obtained prior to the crash, e.g., by an anticipatory sensor, and upon the making of such a determination, triggering an inflator to release gas into the airbag(s) to thereby inflate the same at a first inflation rate, determining in another manner that a crash requiring an airbag will occur or is occurring and, upon the making of such a determination, affecting the inflator such that an additional quantity of gas is released thereby into the airbag(s) to thereby inflate the same at a second inflation rate greater than the first inflation rate. Thus, the airbag is inflated either at the first inflation rate, i.e., if the conditions do not warrant a more powerful inflation, or the second, higher inflation rate, i.e., if the conditions warrant an inflation of the airbags as rapidly as possible. The inflator may comprise a first and second inflator each of which produces gas and directs the gas into the airbag(s) and which are independent of one another such that the first inflator may be triggered by the initial determination of a crash requiring the airbag deployment without triggering of the second inflator and the second inflator may be triggered by the subsequent determination of a crash requiring airbag deployment without triggering of the first inflator.

The airbag passive restraint system for protecting an occupant sitting in the seat adjacent the side door in accordance with the invention may comprise one or more airbag(s) arranged to be inflated between the occupant and the side door, sensor means for detecting that a crash requiring deployment of the airbag(s) is required, inflator means for releasing a gas into the airbag(s) to inflate the same and which are coupled to the sensor means and triggered thereby to release gas into the airbag(s) in response to the detection by the sensor means of a crash requiring deployment of the airbag(s), a seatbelt coupled to the seat for restraining the occupant on the seat and occupant displacement permitting means arranged in connection with the seat for permitting the occupant to be displaced away from the side door upon inflation of the airbag(s) and thereby increase the space between the occupant and the side door.

The occupant displacement permitting means may take a number of different forms all of which serve to enable the occupant to be displaced away from the side door, and if applied in conjunction with an airbag inflating between the side door and the occupant, the inflating airbag may provide a force which serves to actually displace the occupant away from the side door. One embodiment of the occupant displacement permitting means comprises slack introduction means arranged in connection with the seatbelt for introducing a controlled amount of slack into the seatbelt. Alternatively, the occupant displacement permitting means comprise means for changing an anchorage point of the seatbelt from a first anchorage point to a second anchorage point upon inflation of the airbag, both of which may be arranged on a side of the seat away from the side door. The second anchorage point is permanently fixed to the vehicle whereas the first anchorage point is defined by a strip permanently fixed to the vehicle, a first member connected thereto, and a second member having a first position connected to the first member in which the seatbelt is retained at the first anchorage point and a second position apart from the first member in which the seatbelt is not retained at the first anchorage point. Separation means, such an explosive bolt assembly, are coupled to the sensor and move the second member from the first position to the second position so that the seatbelt is no longer retained at the first anchorage point and the displacement of the occupant is not hindered by the seatbelt.

In another embodiment, the system includes mounting means for mounting the airbag adjacent the occupant and the sensor is an anticipatory sensor structured and arranged to detect that a crash requiring deployment of the airbag is required based on data obtained prior to the crash such that the inflator means are triggered to release gas into the airbag prior to the start of the crash. In this case, the occupant displacement permitting means are operatively associated with the anticipatory sensor and the seat to increase the space between the occupant and the side door upon inflation of the airbag. The occupant displacement permitting means may comprise means for laterally displacing the seat away from the side door such as one or more rail mechanisms, each including a first member having a guide channel arranged in connection with the seat or the vehicle and a second member positioned for movement in the guide channel arranged in the other of the seat and the vehicle. Alternatively, the occupant displacement permitting means comprise means for rotating the seat about the vehicle roll axis, possibly also by rail mechanisms, means for rotating the seat about the vehicle yaw axis or means for lifting the seat vertically. The seat lifting means may comprise a first plate attached to the seat, a second plate attached to the vehicle and hingedly attached to the first plate, and a clamp for releasably retaining the first plate in connection with the second plate.

Any of the airbag passive restraint systems described herein may be used in conjunction with the variable inflation rate inflator system described above, and may be used in conjunction with one another to optimize protection for the occupant.

In conjunction with the airbag passive restraint system for protecting an occupant sitting in the seat adjacent the side door described above, the present invention also envisions a method for protecting such an occupant. Such a method would include the steps of detecting that a crash requiring deployment of one or more airbags is required, if so, releasing a gas into the airbag(s) to inflate the same and then in before, during or after the gas is released into the airbag, causing the occupant to be displaced away from the side door upon inflation of the airbag(s) to thereby increase the space between the occupant and the side door. The manner in which the occupant is caused to be displaced away from the side door may take any of the forms described herein.

Other methods for protecting an adjacent occupant in a side impact within the scope of the invention includes the steps of mounting an airbag module comprising a housing and an inflatable airbag arranged within the housing in combination with a seat back, detecting that a side impact requiring deployment of the airbag is required based on data obtained prior to the crash, e.g., by an anticipatory sensor, and then inflating the airbag in the event a side impact requiring deployment of the airbag is detected prior to the start of the impact.

Another possible method entails the use of an externally deployable airbag system for protecting the occupant in a side impact with an impacting object. This method would include the steps of determining that a side impact requiring deployment of an airbag outside of the vehicle between the side of the vehicle and the impacting object is required based on data obtained prior to the crash, and then inflating the airbag in the event a side impact requiring deployment of the airbag is detected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overhead view of a vehicle about to be impacted in the side by an approaching vehicle showing a wave transmitter part of the anticipatory sensor system.

FIG. 1A is a perspective view of a vehicle about to impact the side of another vehicle showing the location of the various parts of the anticipatory sensor system of this invention.

FIG. 2 is an overhead view of a vehicle about to be impacted in the front by an approaching vehicle showing a wave transmitter part of the anticipatory sensor system.

FIG. 3A a plan front view of the front of a car showing the headlights, radiator grill, bumper, fenders, windshield, roof and hood.

FIG. 3B a plan front view of the front of a truck showing the headlights, radiator grill, bumper, fenders, windshield, roof and hood.

FIG. 4 is an overhead view of a vehicle about to be impacted in the side by an approaching vehicle showing an infrared radiation emanating from the front of the striking vehicle and an infrared receiver part of the anticipatory sensor system.

FIG. 5 is a side plan view with portions cutaway and removed of a dual inflator airbag system with two airbags with one airbag lying inside the other.

FIG. 6 is a perspective view of a seatbelt mechanism illustrating a device to release a controlled amount of slack into seatbelt allowing an occupant to be displaced.

FIG. 7 is a front view of an occupant being restrained by a seatbelt having two anchorage points on the driver's right side where the one is released allowing the occupant to be laterally displaced during the crash.

FIG. 7A is an expanded view of the release mechanism within the circle designated 7A in FIG. 7.

FIG. 7B is a view of the apparatus of FIG. 7A within the circle designated 7B and rotated 90 degrees showing the release mechanism.

FIG. 8 is a front view of an occupant being restrained by a seatbelt integral with seat so that when seat moves during a crash with the occupant, the belt also moves allowing the occupant to be laterally displaced during the crash.

FIG. 9A is a front view of an occupant being restrained by a seatbelt and a linear airbag module (930) attached to seat back to protect entire occupant from his pelvis to his head.

FIG. 9B is a view of the system of FIG. 9A showing the airbag in the inflated condition.

FIG. 10A is a front view of an occupant being restrained by a seatbelt and where the seat is displaced toward vehicle center by deploying airbag in conjunction with other apparatus.

FIG. 10B is a front view of an occupant being restrained by a seatbelt and where the seat is rotated about vertical axis in conjunction with other apparatus.

FIG. 10C is a front view of an occupant being restrained by a seatbelt and where the seat is rotated about longitudinal axis in conjunction with other apparatus.

FIG. 11A is a perspective view with portions cutaway and removed of a vehicle about to impact the side of another vehicle showing an airbag stored within the side door of the target vehicle prior to being released to cushion the impact of the two vehicles.

FIG. 11B is a view of the apparatus of FIG. 11A after the airbag has deployed.

FIG. 12 is a schematic drawing of the variable inflation inflator system in accordance with the invention using two inflators.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the accompanying drawings wherein like reference numerals refer to the same or similar elements, FIG. 1 is an overhead view of a vehicle 110 about to be impacted in the side by an approaching vehicle 120 where vehicle 110 is equipped with an anticipatory sensor system in accordance with the invention including a wave transmitter 130 which transmits waves 132 toward the approaching vehicle 120. A perspective view of vehicle 110 is shown in FIG. 1A and illustrates the transmitter 130 connected to an electronic module 140 (this connection being symbolized by the dotted lines between the transmitter 130 and the module 140 which may represent a wire). Module 140 contains circuitry means 142 to drive the transmitter 130 to transmit waves and circuitry means 144 coupled to wave receivers 134,136, which receive the returned waves and convert the same into signals, to process the signals from receivers 134 and 136 representative of the returned waves. Circuitry 144 contains a neural computer 145 that performs the pattern recognition determination based on signals from the receivers 134 and 136. Receivers 134,136 are positioned are either side of transmitter 130, although the presence of two such receivers and the positioning on both sides thereof is not critical or essential to the invention and different amounts of receivers and different relative positions to the transmitter are encompassed within the scope and spirit of invention.

Throughout the description herein, the term “approaching” when used as an object or vehicle approaching another will mean the relative motion of the object toward the vehicle having the anticipatory sensor system. Thus, in a side impact with a tree, the tree will be considered as approaching the side of the vehicle and impacting the vehicle. In other words, the coordinate system used in general will be a coordinate system residing in the target vehicle. The “target” vehicle is the vehicle that is being impacted. This convention permits a general description to cover all of the cases such as where (i) a moving vehicle impacts into the side of a stationary vehicle, (ii) where both vehicles are moving when they impact, or (iii) where a vehicle is moving sideways into a stationary vehicle, tree or wall.

In a preferred implementation, transmitter 130 is an ultrasonic transmitter operating at a frequency of approximately 40 kHz, although other frequencies could be used. Similarly, receivers 134 and 136 are ultrasonic receivers or transducers and receive the reflected ultrasonic waves from vehicle 120.

A detailed discussion of pattern recognition technology as applied to the monitoring and identification of occupants and objects within a vehicle is discussed in detail in Breed et al co-pending U.S. patent application Ser. No. 08/640,068 filed Apr. 30, 1996 and included herein by reference. Although the application herein is for the identification of objects exterior to the vehicle, many of the same technologies, principles and techniques are applicable.

An example of such a pattern recognition system using neural networks using sonar is discussed in two papers by Gorman, R,. P. and Sejnowski, T. J. “Analysis of Hidden Units in a Layered Network Trained to Classify Sonar Targets”, Neural Networks, Vol. 1. pp 75-89, 1988, and “Learned Classification of Sonar Targets Using a Massively Parallel Network”, IEEE Transactions on Acoustics, Speech, and Signal Processing, Vol. 36, No. 7, July 1988.

“Pattern recognition” as used herein will mean any system which processes a signal that is generated by an object, or is modified by interacting with an object, in order to determine which one of a set of classes that the object belongs to. Such a system might determine only that the object is or is not a member of one specified class, or it might attempt to assign the object to one of a larger set of specified classes, or find that it is not a member of any of the classes in the set. The signals processed are generally electrical signals coming from transducers which are sensitive to either acoustic or electromagnetic radiation and if electromagnetic they can be either visible light, infrared, ultraviolet or radar.

A “trained” pattern recognition system as used herein will mean a pattern recognition system that is trained on data representing different operating possibilities. For example, the training data may constitute a number of sets of a signal from receiver 134 represented the returned waves received thereby, a signal from receiver 136 representing the returned waves received thereby and one or more properties of the approaching object, e.g., its form or shape, size or weight, identity, velocity, breadth and relative distance. Once trained, the trained pattern recognition system will be provided with the signals from receivers 134,136 and categorize the signals that would lead to a determination by the system of the property or properties of the approaching object, e.g., its size or identity.

“To identify” as used herein will mean to determine that the object belongs to a particular set or class. The class may be one containing all trucks of a certain size or weight, one containing all trees, or all walls. In the case where a particular vehicle type is to be recognized, the set or class will contain only a single element, the particular vehicle type to be recognized.

Some examples follow:

In a passive infrared system, a detector receives infrared radiation from an object in its field of view, in this case the approaching object is most likely another vehicle, and processes the received infrared radiation radiating from the vehicle's engine compartment. The anticipatory sensor system then processes the received radiation pattern to determine the class of vehicle, and, along with velocity information from another source, makes an assessment of the probable severity of the pending accident and determines if deployment of an airbag is required. This technology can provide input data to a pattern recognition system but it has limitations related to temperature. The sensing of a non-vehicle object such as a tree, for example, poses a particular problem. The technology may also fail to detect a vehicle that has just been started especially if the ambient temperature is high. Nevertheless, for use in the identification of approaching vehicles the technology can provide important information especially if it is used to confirm the results from another sensor system.

In a laser optical system, the transmitter 130 comprises an infrared laser beam which is used to momentarily illuminate an object as illustrated in FIG. 1 where transmitter 130 is such a laser beam transmitter. In some cases, a charge coupled device (a type of TV camera), or a CMOS optical sensor array, is used to receive the reflected light and would be used as one or both of the receivers 132 and 134. The laser can either be used in a scanning mode, or, through the use of a lens, a cone of light can be created which covers a large portion of the object. In each case, a pattern recognition system, as defined above, is used to identify and classify the illuminated object and its constituent parts. The scanning implementation of the laser system has an advantage that the displacement of the object can be calculated by triangulation of the direction of the return light from the transmitted light providing the sensor and transmitter as displaced from one another. This system provides the most information about the object and at a rapid data rate. Its main drawback is cost which is considerably above that of ultrasonic or passive infrared systems and the attenuation that results in bad weather conditions such as heavy rain, fog or snow storms. As the cost of lasers comes down in the future, this system will become more competitive. The attenuation problem is not as severe as might be expected since the primary distance of concern for anticipatory sensors as described here is usually less than three meters and it is unlikely that a vehicle will be operated with a visibility of only a few meters. If the laser operates in the infrared region of the spectrum, the attenuation from fog is less than if it is operated in the visible part of the spectrum.

Radar systems have similar properties to the laser system discussed above with the advantage that there is less attenuation in bad weather. The wavelength of a particular radar system can limit the ability of the pattern recognition system to detect object features smaller than a certain size. This can have an effect in the ability of the system to identify different objects and particularly to differentiate between different truck and automobile models. It is also more difficult to use radar in a triangulation system to obtain a surface map of the illuminated object as can be done with an infrared laser.

The ultrasonic system is the least expensive and potentially provides less information than the laser or radar systems due to the delays resulting from the speed of sound and due to the wave length which is considerably longer than the laser systems. The wavelength limits the detail that can be seen by the system. In spite of these limitations, as shown in the above referenced Breed et al patent application Ser. No. 08/640,068, ultrasonics can provide sufficient timely information to permit the position and velocity of an approaching object to be accurately known and, when used with an appropriate pattern recognition system, it is capable of positively determining the class of the approaching object. One such pattern recognition system uses neural networks and is similar to that described in the papers by Gorman et al and in the rear facing child seat recognition system referenced and described in the Breed et al patent application referenced above.

A focusing system, such as used on some camera systems, could be used to determine the position of an approaching vehicle when it is at a significant distance away but is too slow to monitor this position just prior to a crash. This is a result of the mechanical motions required to operate the lens focusing system. By itself, it cannot determine the class of the approaching object but when used with a charge coupled, or CMOS, device plus infrared illumination for night vision, and an appropriate pattern recognition system, this becomes possible.

From the above discussion, it can be seen that the addition of sophisticated pattern recognition means to any of the standard illumination and/or reception technologies for use in a motor vehicle permits the development of an anticipatory sensor system which can identify and classify an object prior to the actual impact with the vehicle.

The application of anticipatory sensors to frontal impact protection systems is shown in FIG. 2 which is an overhead view of a vehicle 110 about to be impacted in the front by an approaching vehicle 120. In a similar manner as in FIG. 1, a transmitter 160 transmits waves 162 toward vehicle 120. These waves are reflected off of vehicle 120 and received by receiving transducers 164 and 166 positioned on either side of transmitter 160.

FIG. 3A illustrates the front of an automobile 310 and shows preferred locations for transmitting transducer 160 and receiving transducers 164 and 166, i.e., the transmitter 160 below the grill and the receivers 164,166 on each side of the grill. FIG. 3A also illustrates the distinctive features of the vehicle which cause a distinct pattern of reflected waves which will differ from that of a truck 320, for example, as shown in FIG. 3B. In some pattern recognition technologies, the researcher must determine the distinctive features of each object to be recognized and form rules that permit the system to recognize one object from another of a different class. An alternative method is to use artificial neural network technology wherein the identification system is trained to recognize different classes of objects. In this case, a training session is conducted where the network is presented with a variety of objects and told to which class each object belongs. The network then learns from the training session and, providing a sufficient number and diversity of training examples are available, the network is able to categorize other objects which have some differences from those making up the training set of objects. The system is quite robust in that it can still recognize objects as belonging to a particular class even when there are significant differences between the object to be recognized and the objects on which the system was trained.

Once a neural network has been sufficiently trained, it is possible to analyze the network and determine the “rules” which the network evolved. These rules can then sometimes be simplified or generalized and programmed as a fuzzy logic algorithm. Alternately, a neural computer can be programmed and the system implemented on a semiconductor chip as available from Motorola.

The anticipatory sensor system must also be able to determine the distance, approach velocity and trajectory of the impacting object in addition to the class of objects to which it belongs. This is easily done with acoustic systems since the time required for the acoustic waves to travel to the object and back determine its distance based on the speed of sound. With radar and laser systems, the waves usually need to be modulated and the phase change of the modulation determined in order to determine the distance to the object as discussed in more detail in U.S. patent application Ser. No. 08/040,978 filed Mar. 31, 1993 to Breed et al and included herein by reference. Since the same distance measurement techniques are used here as in the two above referenced patent applications, they will not be repeated here.

There is a radar chip on the market that permits the distance determination based on the time required for the radar waves to travel to the object and back. This technology was developed by Amerigon Inc. of Burbank Calif. and is being considered for other automotive applications such as constant distance cruise control systems and backing-up warning systems.

FIG. 3A is a plan front view of the front of a car showing the headlights, radiator grill, bumper, fenders, windshield, roof and hood and other objects which reflect a particular pattern of waves whether acoustic or electromagnetic. Similarly, FIG. 3B is a plane frontal view of the front of a truck showing the headlights, radiator grill, bumper, fenders, windshield, roof and hood illustrating a significantly different pattern. Neural network pattern recognition techniques using software available from NeuralWare Corp. of Pittsburgh, Pa. can be used to positively classify trucks as a different class of objects from automobiles and further to classify different types of trucks giving the ability to predict accident severity based on truck type and therefore likely mass, as well as velocity. Other software tools are also commercially available for creating neural networks and fuzzy logic systems capable of recognizing patterns of this type.

In FIG. 4, an overhead view of a vehicle 110 about to be impacted in the side by an approaching vehicle 120 in a perpendicular direction is illustrated where infrared radiation 432 is radiating from the front of the striking vehicle 120. An infrared receiver 434 arranged on the side of vehicle 110 receives this radiation for processing as described above.

The anticipatory sensor system described and illustrated herein is mainly used when the pending accident will cause death or serious injury to the occupant. Since the driver will no longer be able to steer or apply the brakes to the vehicle after deployment of an airbag which is sufficiently large to protect him in serious accidents, it is important that this large airbag not be deployed in less serious accidents where the driver's injuries are not severe. Nevertheless, it is still desirable in many cases to provide some airbag protection to the driver. This can be accomplished as shown in FIG. 5 which is a side plane view with portions cutaway and removed of a dual inflator airbag system, shown generally as 500, with an airbag 505 which in essence comprises two separate airbags 510 and 520 with one airbag 510 lying inside the other airbag 520. Although a single inflator having a variable inflation rate capability can be used, FIG. 5 illustrates the system using two discrete inflators 530 and 540 which may be triggered independently or together to thereby provide a variable inflation rate of the airbag 505. Inflator 540 and associated airbag 520 are controlled by the anticipatory sensor system described herein and the inflator 530 and associated airbag 510 could also be initiated by the same system. In a less severe accident, inflator 530 can be initiated also by the anticipatory sensor without initiating inflator 540 or, alternately, inflator 530 could be initiated by another sensor system such as described U.S. Pat. No. 5,231,253 to Breed et al. Each inflator 530,540 contains standard materials therefor, e.g., an initiator, a gas propellant. Thus, the variable inflation rate inflator system for inflating the airbag 505 comprises inflators 530,540 for producing a gas and directing the gas into the airbag 505, and crash sensors (as described in any of the embodiments herein or otherwise available) for determining that a crash requiring an airbag will occur or is occurring and, upon the making of such a determination, triggering the inflator(s) 530 and/or 540 to produce gas and direct the gas into the airbag 505 to thereby inflate the same at a variable inflation rate, which depends on whether only inflator 530 is triggered, only inflator 540 is triggered or both inflators 530,540 are triggered (See FIG. 12). More particularly, the inflator 540 may be associated with an anticipatory crash sensor to be triggered thereby and the inflator 530 may be associated with the anticipatory crash sensor or another different sensor, such as one which detects the crash only after it has occurred. In this manner, inflator 540 will be triggered prior to inflator 530 and inflator 530, if triggered, will supply an additional amount of gas into the airbag 505. Although the description above is based on the use of two inflators, the same result can be obtained through the use of a variable outflow port or vent from the airbag 505. This has the advantage that only a single inflator is required and the decision as to how much gas to leave in the airbag can be postponed.

When the large airbag 520 is inflated from the driver's door, for example, it will attempt to displace the occupant away from the vehicle door. If the seatbelt attachment points do not also move, the occupant will be prevented from moving by the seatbelt and some method is required to introduce slack into the seatbelt or otherwise permit him to move. Such a system is shown in FIG. 6 which is a perspective view of a seatbelt mechanism where a device releases a controlled amount of slack into seatbelt allowing an occupant to be displaced. The seatbelt spool mechanism incorporating the slack inducer is shown generally as 600 in FIG. 6 and includes a seatbelt 602 only a portion of which is shown, a housing 604 for the spool mechanism, a spool 606 containing several wound layers of seatbelt material 602. Also attached to the spool 606 is a sheave 608 upon which is wound a cable 610. Cable 610 is connected to a piston 622 of an actuator 620. Piston 622 is positioned within a cylinder 624 of the actuator 620 so that a space is defined between a bottom of the cylinder 624 and the piston 622 and is able to move within cylinder 624 as described below.

When the anticipatory sensor system decides to deploy the airbag, it also sends a signal to the seatbelt slack inducer system of FIG. 6. This signal is in the form of an electric current which passes through a wire 632 and is of sufficient magnitude to initiate pressure generating means for generating a pressure in the space between the piston 622 and the cylinder 624 to force the piston 622 in a direction to cause the sheave 608 to rotate and thus the spool 606 to rotate and unwind the seatbelt therefrom. More specifically, the electric current through wire 632 ignites a squib 634 arranged in connection with a propellant housing 630. Squib 634 in turn ignites propellant 636 situated within housing 630. Propellant 636 burns and produces gas which pressurizes chamber 638 defined in housing 630, which is in fluid communication with the space at a bottom 623 of the cylinder 624 between the cylinder 624 and the piston 622, and pressurizes cylinder 624 below piston 622. When subjected to this pressure, piston 622 is propelled upward within cylinder 624, pulling cable 610 and causing sheave 608 to rotate in the counterclockwise direction as shown in FIG. 6. This rotation causes the spool 606 to also rotate causing the belt 602 to spool off of spool 606 and thereby inducing a controlled amount of slack into the belt and thus permitting the occupant to be displaced to the side. In some cases, it may not be necessary to control the amount of slack introduced into the seatbelt and a simpler mechanism which releases the seatbelt can be used.

An alternate system is shown in FIG. 7 which is a frontal view of an occupant 710 being restrained by a seatbelt 720 having two anchorage points 730 and 732 on the right side of the driver where the one 730 holding the belt at a point closest to the occupant 710 is released allowing the occupant 710 to be laterally displaced to the left in the figure during the crash. A detail of the release mechanism 730 taken within the circle 7A is shown in FIG. 7A. The mechanism shown generally as 730 comprises an attachment bolt 744 for attaching the mechanism to the vehicle tunnel sheet-metal 740. Bolt 744 also retains a metal strip 742 connected to member 737. Member 737 is in turn attached to member 739 by means of explosive bolt assembly 736. Member 739 retains the seatbelt 720 by virtue of pin 738 (FIG. 7B). A stop 752 placed on belt 720 prevents the belt from passing through the space between pin 738 and member 739 in the event that the primary anchorage point 732 fails. Upon sensing a side impact crash, a signal is sent through a wire 734 which ignites explosive bolt 736 releasing member 737 from 739 and thereby inducing a controlled amount of slack into the seatbelt.

In some implementations, the vehicle seat is so designed that in a side impact, it can be displaced or rotated so that both the seat and occupant are moved away from the door. In this case, if the seatbelt is attached to the seat, there is no need to induce slack into the belt as shown in FIG. 8. FIG. 8 is a frontal view of an occupant 810 being restrained by a seatbelt 820 integral with seat 830 so that when seat 830 moves during a crash with the occupant 810, the seatbelt 820 and associated attachments 842, 844, 846 and 848 also move with the seat allowing the occupant 810 to be laterally displaced during the crash.

Various airbag systems have been proposed for protecting occupants in side impacts. Some of these systems are mounted within the vehicle seat and consist of a plurality of airbag modules when both the head and torso need to be protected. An illustration of the use of this module is shown in FIG. 9A, which is a frontal view of an occupant 910 being restrained by a seatbelt 920 and a linear airbag module 930, of the type described in the aforementioned patent application, including among other things a housing 935 and an inflatable airbag 932 arranged therein and associated inflator means. This linear module is mounted by appropriate mounting means to the side of seat back 940 to protect entire occupant 910 from his pelvis to his head. An anticipatory sensor may be provided as described above, i.e., one which detects that a side impact requiring deployment of the airbag is required based on data obtained prior to the crash and initiates inflation of the airbag by the inflator means in the event a side impact requiring deployment of the airbag is detected prior to the start of the impact.

Airbag module 930 may extend substantially along a vertical length of the seat back 940 as shown, and the airbag 932 in the housing 935 may be attached to the seat-back 940 or integral therewith.

A view of the system of FIG. 9A showing the airbag 932 in the inflated condition is shown in FIG. 9B.

In FIG. 10A, a frontal view of an occupant 1010 being restrained by a seatbelt 1020 and wherein the seat 1050 is displaced toward vehicle center by deploying airbag 1040 is shown. In this case, the seatbelt 1020 is attached to the seat 1050 as described above with reference to FIG. 8. In this case, rail mechanisms 1062 and 1064 permit the seat to be displaced away from the door under the force produced by the deploying airbag 1040. Rail mechanisms 1062,1064 may include a first member having a guide channel and a second member having a projection positioned for movement in the guide channel of the first member.

In FIG. 10B, a frontal view of an occupant 1010 being restrained by a seatbelt 1020 and wherein the seat 1050 is rotated toward vehicle center, i.e., substantially about an axis perpendicular to a horizontal plane of the vehicle, by deploying airbag 1040 is shown. In this case, the seatbelt 1020 is attached to the seat 1050 as described above with reference to FIG. 8. In this case, rail mechanisms 1066 and mounting locations 1068 permit the seat to be rotated away from the door under the force produced by the deploying airbag 1040. This figure is shown with the occupant rotated 90 degrees from initial position, this amount of rotation may be difficult for all vehicles. However, some degree of rotation about the vertical axis is possible in most vehicles. Rail mechanisms 1066 may include a first member having a curved guide channel and a second member having a projection positioned for a curving or rotational movement in the guide channel of the first member.

In an alternate case where there is sufficient space for the occupant's legs and feet, the seat 1050 can be rotated as shown in FIG. 10C, i.e., substantially about an axis oriented in a longitudinal direction of the vehicle. The rotating mechanism comprises a hinged assembly of two plates 1052 and 1054, with plate 1052 attached to the vehicle floorpan and plate 1054 attached to the vehicle seat 1050. The two plates are held together by a suitable clamp 1058 which is released by the sensor at the same time the airbag is deployed. Many of the techniques disclosed above will not work well for some of today's small vehicles. They are applicable in vans, sport utility vehicles, some small trucks and some minivans. For other vehicles, an externally deployed airbag may be the only assured solution.

Once an anticipatory sensor system is in place, it becomes possible to consider deployment of an airbag external to the vehicle. This possibility has appeared in the automobile safety literature in the past but it has not been practical until the impacting object can be identified and an assessment of the probable severity of the accident made. For prior art systems, it has not been possible to differentiate between a plastic sand-filled construction barrier or a cardboard box, for example, neither of which would not result in a serious accident and a concrete pillar, tree or wall which would. With the development of the pattern recognition systems described herein, and in the above referenced patent applications, this problem has been solved and the use of an external airbag now becomes feasible.

Such a system adapted for side impact protection is shown in FIG. 11A which is a perspective view with portions cutaway and removed of a vehicle 1110 about to be impacted in the side by another vehicle 1120. An airbag module is shown generally as 1180 mounted to the side door of the vehicle 1110 prior to inflation of an airbag 1182 arranged in the airbag module 1180. A portion of the side door of vehicle 1110 has been cutaway to permit viewing of the airbag module 1180. The vehicle 1110 contains a strong support beam 1160 arranged in a longitudinal direction of the vehicle at least partially within the side door(s) 1155 and which provides a reaction surface along with the vehicle door 1155 for the airbag. Upon initiation by the anticipatory sensor, a deployment door, not shown, is opened in an external door panel 1156 by any of a number of methods such as pyrotechnically, permitting the airbag 1182 to emerge from the vehicle door 1155 as shown in FIG. 11B, the airbag 1182 being inflated by inflator means responsive to the detection by the anticipatory sensor that a side impact requiring deployment of the airbag is required.

Through a system such as illustrated in FIGS. 11A and 11B, the accident can be substantially cushioned prior to engagement between the vehicle and the impacting object. By this technique, an even greater protection can be afforded the occupant especially if an internal airbag is also used. This has the further advantage that the occupant may not have to be displaced from behind the steering wheel and thus the risk to causing an accident is greatly reduced. It also may be the only system which will work with some of today's small vehicles.

Although several preferred embodiments are illustrated and described above, there are possible combinations using other geometries, sensors, materials and different dimensions for the components that perform the same functions. This invention is not limited to the above embodiments and should be determined by the following claims. 

What is claimed is:
 1. A motor vehicle having a passive restraint system including at least first and second airbags and an inflator system for inflating said at least one airbag, said inflator system comprising: inflator means for controlling accumulation of a gas in said at least one airbag and thus inflation of said at least one airbag, said inflator means comprising a first inflator means structured and arranged to produce gas and direct the gas into said first airbag and a second inflator means structured and arranged to produce gas and direct the gas into said second airbag, a first anticipatory crash sensor for determining that a crash requiring an airbag will occur based on data obtained prior to the crash and, upon the making of such a determination, triggering said first inflator means to release gas into said first airbag to thereby inflate said at least one airbag at a first inflation rate; and a second crash sensor for determining that a crash requiring an airbag will occur or is occurring and, upon the making of such a determination, triggering said second inflator means to release gas into said second airbag to thereby inflate said at least one airbag at a second inflation rate greater than said first inflation rate.
 2. The invention in accordance with claim 1, wherein said first airbag defines an interior and said second airbag is arranged in the interior of said first airbag.
 3. The invention in accordance with claim 1, wherein said first and second inflator means are operatively independent of one another such that said first inflator means may be triggered by said first anticipatory crash sensor without triggering of said second inflator means and said second inflator means may be triggered by said second crash sensor without triggering of said first inflator means.
 4. The invention in accordance with claim 1, wherein the vehicle includes a side door and a seat, at least one of said first and second airbags being arranged to inflate between the occupant and the side door, the passive restraint system further comprising occupant displacement permitting means arranged in connection with the seat for permitting the occupant to be displaced away from the side door upon inflation of said at least one airbag and thereby increase the space between the occupant and the side door.
 5. The invention in accordance with claim 4, wherein the passive restraint system further comprises a seatbelt coupled to the seat for restraining the occupant on the seat, said occupant displacement permitting means comprising slack introduction means arranged in connection with said seatbelt for introducing a controlled amount of slack into said seatbelt.
 6. The invention in accordance with claim 5, wherein said slack introduction means comprise a spool on which an end of said seatbelt is wound, a sheave attached to said spool, a cable wound around said sheave, an actuator including a cylinder, a piston connected to said cable and movable within said cylinder and means defining a space between a bottom of said cylinder and said piston, and pressure generating means for generating a pressure in said space to force said piston in a direction to cause said sheave to rotate and thus said spool to rotate and unwind said seatbelt from said spool.
 7. The invention in accordance with claim 6, wherein said pressure generating means comprise a housing containing propellant, a squib arranged in connection with said housing and being activated by at least one of said first anticipatory crash sensor and said second crash sensor to ignite said propellant and thereby produce pressurized gas, and a chamber in flow communication with said propellant to receive the pressurized gas, said chamber being in flow communication with said space in said actuator.
 8. The invention in accordance with claim 1, wherein the vehicle includes a seat having a back portion, at least one of aid first and second airbags being arranged in said back portion of the seat.
 9. The invention in accordance with claim 8, wherein said at least one airbag is attached to said back portion of the seat.
 10. The invention in accordance with claim 8, wherein said at least one airbag is integral with said back portion of the seat.
 11. The invention in accordance with claim 1, wherein said inflator system further comprises an airbag module having a housing, at least one of said first and second airbags being arranged in said housing.
 12. The invention in accordance with claim 11, wherein the vehicle includes a seat having a back portion, said at least one airbag being arranged in said back portion of the seat.
 13. The invention in accordance with claim 12, wherein said airbag module extends substantially along a vertical length of said back portion of the seat.
 14. The invention in accordance with claim 1, wherein at least one of said first and second airbags is arranged to inflate outside of the vehicle.
 15. The invention in accordance with claim 14, wherein said at least one airbag is arranged in an airbag module and said airbag module is mounted in a side door of the vehicle.
 16. A method for inflating at least one airbag arranged in a vehicle, the vehicle including a side door, a seat and a seatbelt coupled to the seat for restraining an occupant on the seat, a first one of the at least one airbag being arranged to inflate between the occupant and the side door, the method comprising the steps of: making a first determination by means of an anticipatory crash sensor that a crash requiring deployment of one or more airbags will occur based on data obtained prior to the crash, upon the making of the first determination, producing gas by means of a first inflator means and releasing the gas into the first airbag, making a second, separate determination by means of a second crash sensor that a crash requiring an airbag will occur or is occurring, upon the making of the second determination, producing an additional quantity of gas by means of a second inflator means and releasing the additional quantity of gas into the first airbag, and displacing the occupant away from the side door upon inflation of the first airbag to thereby increase the space between the occupant and the side door.
 17. The invention in accordance with claim 16, further comprising the step of: arranging the first and second inflator means to be operatively independent of one another such that the first inflator means may be triggered without triggering of the second inflator means and the second inflator means may be triggered without triggering of the first inflator means.
 18. The invention in accordance with claim 16 wherein the step of displacing the occupant away from the side door comprises the step of introducing a controlled amount of slack into the seatbelt.
 19. The invention in accordance with claim 16, further comprising the step of: arranging an additional airbag in a back portion of a seat of the vehicle.
 20. The invention in accordance with claim 16, further comprising the step of: arranging an additional airbag in a housing of an airbag module extending substantially along a vertical length of a back portion of a seat of the vehicle.
 21. The invention in accordance with claim 16, further comprising the step of: arranging an additional airbag to inflate outside of the vehicle.
 22. A motor vehicle having a passive restraint system including first and second airbags and an inflator system for inflating said first and second airbags, said inflator system comprising: inflator means for inflating said first and second airbags, a first anticipatory crash sensor for determining that a crash requiring inflation of said first airbag will occur based on data obtained prior to the crash and, upon the making of such a determination, causing said inflator means to inflate said first airbag, said first crash sensor and said inflator means being structured and arranged such that said first airbag is inflated by said inflator means based solely on a determination by said first crash sensor that inflation of said first airbag is required, and a second crash sensor for determining that a crash requiring inflation of said second airbag will occur or is occurring and, upon the making of such a determination, causing said inflator means to inflate said second airbag, said second crash sensor and said inflator means being structured and arranged such that said second airbag is inflated by said inflator means based solely on a determination by said second crash sensor that inflation of said second airbag is required.
 23. The invention in accordance with claim 22, wherein said second airbag is arranged in said first airbag.
 24. The invention in accordance with claim 22, wherein said inflator means comprise a first inflator means structured and arranged to produce and release gas into said first airbag and a second inflator means, separate from said first inflator means, structured and arranged to produce and release gas into said second airbag.
 25. A motor vehicle having a passive restraint system including an airbag and a variable inflation rate inflator system for inflating said airbag, the vehicle including a side door and a seat, said airbag being arranged to inflate between the occupant and the side door, said variable inflation rate inflator system comprising: inflator means for releasing a gas into said airbag; a first anticipatory crash sensor for determining that a crash requiring an airbag will occur based on data obtained prior to the crash and, upon the making of such a determination, triggering said inflator means to release gas into said airbag to thereby inflate said airbag at a first inflation rate; and a second crash sensor for determining that a crash requiring an airbag will occur or is occurring and, upon the making of such a determination, changing the rate at which gas accumulates in said airbag to thereby inflate said airbag at a second inflation rate different than said first inflation rate; said passive restraint system further comprising occupant displacement permitting means arranged in connection with the seat for permitting the occupant to be displaced away from the side door upon inflation of said airbag and thereby increase the space between the occupant and the side door, and a seatbelt coupled to the seat for restraining the occupant on the seat, said occupant displacement permitting means comprising slack introduction means arranged in connection with said seatbelt for introducing a controlled amount of slack into said seatbelt.
 26. The invention in accordance with claim 25, wherein said slack introduction means comprise a spool on which an end of said seatbelt is wound, a sheave attached to said spool, a cable wound around said sheave, an actuator including a cylinder, a piston connected to said cable and movable within said cylinder and means defining a space between a bottom of said cylinder and said piston, and pressure generating means for generating a pressure in said space to force said piston in a direction to cause said sheave to rotate and thus said spool to rotate and unwind said seatbelt from said spool.
 27. The invention in accordance with claim 26, wherein said pressure generating means comprise a housing containing propellant, a squib arranged in connection with said housing and being activated by at least one of said first anticipatory crash sensor and said second crash sensor to ignite said propellant and thereby produce pressurized gas, and a chamber in flow communication with said propellant to receive the pressurized gas, said chamber being in flow communication with said space in said actuator.
 28. A method for inflating an airbag arranged in a vehicle, the vehicle including a side door, a seat and a seatbelt coupled to the seat for restraining the occupant on the seat, the airbag being arranged to inflate between the occupant and the side door, the method comprising the steps of: making a first determination by means of an anticipatory crash sensor that a crash requiring deployment of one or more airbags will occur based on data obtained prior to the crash and, upon the making of such a determination, releasing gas into the airbag, making a second, separate determination by means of a second crash sensor that a crash requiring an airbag will occur or is occurring and, upon the making of such a determination, changing the rate at which gas accumulates in the airbag, and displacing the occupant away from the side door upon inflation of the airbag to thereby increase the space between the occupant and the side door, the step of displacing the occupant away from the side door comprising the step of introducing a controlled amount of slack into the seatbelt.
 29. A motor vehicle having a passive restraint system including an airbag and a variable inflation rate inflator system for inflating said airbag, the vehicle includes a side door and a seat, said airbag being arranged to inflate between the occupant and the side door, said variable inflation rate inflator system comprising: inflator means for controlling accumulation of a gas in said airbag and thus inflation of said airbag, said inflator means comprising a first inflator means structured and arranged to produce gas and direct the gas into said airbag and a second inflator means structured and arranged to produce gas and direct the gas into said airbag, a first anticipatory crash sensor for determining that a crash requiring an airbag will occur based on data obtained prior to the crash and, upon the making of such a determination, triggering said first inflator means to release gas into said airbag to thereby inflate said airbag at a first inflation rate, a second crash sensor for determining that a crash requiring an airbag will occur or is occurring and, upon the making of such a determination, triggering said second inflator means such that an additional quantity of gas is released by said second inflator means into said airbag to thereby inflate said airbag at a second inflation rate greater than said first inflation rate, and occupant displacement permitting means arranged in connection with the seat for permitting the occupant to be displaced away from the side door upon inflation of said airbag and thereby increase the space between the occupant and the side door.
 30. The invention in accordance with claim 29, wherein said first and second inflator means are operatively independent of one another such that said first inflator means may be triggered by said first anticipatory crash sensor without triggering of said second inflator means and said second inflator means may be triggered by said second crash sensor without triggering of said first inflator means.
 31. The invention in accordance with claim 29, wherein the passive restraint system further comprises a seatbelt coupled to the seat for restraining the occupant on the seat, said occupant displacement permitting means comprising slack introduction means arranged in connection with said seatbelt for introducing a controlled amount of slack into said seatbelt.
 32. The invention in accordance with claim 31, wherein said slack introduction means comprise a spool on which an end of said seatbelt is wound, a sheave attached to said spool, a cable wound around said sheave, an actuator including a cylinder, a piston connected to said cable and movable within said cylinder and means defining a space between a bottom of said cylinder and said piston.
 33. The invention in accordance with claim 32, wherein said slack introduction means further comprise pressure generating means for generating a pressure in said space to force said piston in a direction to cause said sheave to rotate and thus said spool to rotate and unwind said seatbelt from said spool.
 34. The invention in accordance with claim 33, wherein said pressure generating means comprise a housing containing propellant and a squib arranged in connection with said housing.
 35. The invention in accordance with claim 34, wherein said squib is arranged to be activated by at least one of said first anticipatory crash sensor and said second crash sensor to ignite said propellant and thereby produce pressurized gas, said pressure generating means further comprising a chamber in flow communication with said propellant to receive the pressurized gas, said chamber being in flow communication with said space in said actuator.
 36. The invention in accordance with claim 29, wherein said variable inflation rate inflator system further comprises an airbag module having a housing, said airbag being arranged in said housing. 